Coded signaling system



Feb. 8, 1949. F. H. NlCH OLSON CODED SIGNALING SYSTEM iled Jan. 25, 1947 2 Sheets-Sheet 1 INVENTORI I Franl ACN olJ'ozz H16 ATTORNEY Feb. 8, 1949.

F. H. NICHOLSON CODED SIGNALING SYSTEM 2 Sheets-Sheet 2 Filed Jan. 25, 1947 ATTO RN EY Patented Feb. 8, I 1 949 CODED SIGNALING SYSTEM Frank H. Nicholson, Penn Township, Allegheny County, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application January 25 1947, Serial No. 724,382

20 Claims. 1

My invention relates to coded signaling apparatus and particularly to improved means for preventing improper sup ly of energy to a code following relay.

In some types of coded signaling systems, as for example, a coded track circuit signaling system, a transmitting relay is located at one end of a pair of conductors, such as the track rails of a section of railway track, and has contacts which are operated between a position in which they connect the winding of a code following relay across the conductors and a position in which they connect a battery or other suitable source of energy across the conductors. In some situations it is desirable to supply from the battery to the conductors energy which is of one polarity at times and is of the other polarity at other times.

An object of this invention is to provide improved circuit means for connecting the battery and the code following relay with the conductors in such manner that energy from the battery will not operate the code following relay in the event the contacts of the transmitting relay are defective or are out of adjustment. 7

A further object of the invention is to provide in a coded signaling system of the type employing feed-back code improved means for supplying impulses of feed-back energy to the conductors.

Another object of 'the invention is to provide in a signaling system of the type described improved means for preventing operation of the code following relay by energy inductively discharged from the conductors on interruption of the supply of an impulse of energy to the conductors.

Other objects of the invention and features of novelty will be apparent from the following description taken in, connection with the accompanying drawings.

In practicing my invention I employ a code fol lowing relay of the polar biased neutral type the contacts of which pick up when and only when energy flows through the relay winding in a selected direction. The code following relay is connected across the conductors when a contact of a transmitter relay is in one of its two positions, while a battery is connected across the conductors when the transmitter relay contact is in the other of its two positions. The connections between the battery and the conductors are governed by contacts of a pole changing relay so that at times energy of one polarity and at other times energy of the other polarity is supplied from the battery to the conductors. The circuits between the battery and the conductors and between the code following relay and the conductors are arranged so that when the contacts of the pole changing relay are positioned to cause energy of either polarity tobe supplied from the battery to the conductors, the energy supplied from the battery to the code following relay in the event the contacts of the transmitter relay overlap will be of the wrong polarity to pick up the contacts of the code following relay. The circuit for connecting the code following relay across the conductors includes front contacts of a relay governed by the transmitter relay so that a positive time interval is provided between the instant at which the circuit of the battery is disconnected from the conductors and the instant at which the code following relay is connected across the conductors to thereby insure that the energy inductively discharged from the conductors on interruption of the circuit of the battery will be dissipated before the code following relay is connected across the conductors.

In the drawings, Fig. 1 is a diagram of a section of railway track equipped with signaling apparatus embodying this invention, and

Figs. 1A, 2 and 3 are diagrams showing modifled arrangements which I may empoy.

Similar reference characters refer to similar parts in each of the several views.

Referring to Fig. l of the drawings there is shown therein a section of railway track having track rails l and 2 which are separated from the rails of adjoining sections by means of insulated joints 3. A code following relay TR and a battery IB are located at one end of the track section and are alternately connected across the track rails by contacts of a transmitter or impulse relay IR. The code following relays RAR and NAR and a battery TB are located at the other end of the track section, and the reays and the battery are alternately connected across the track rails by contacts of the transmitter relay CTM.

The code following relays TR, RAR and NAR are of the polar biased neutral type and each has contacts which are biased to a released position from which they are moved to their picked-up position when and only when energy flows through the relay winding in a selected direction as indicated by the arrow on the relay winding. The relays RAR and NAR are arranged so that they respond to energy of opposite polarity supplied over the track rails, while the relay TR responds to energy which is of the polarity in which the traclgrail l is positive with respect to track rail 2.

The relay TR controls a code detecting relay H which may be employed for any appropriate purpose, as for example, to control a wayside signal, not shown, for governing entrance of traiiic into the track section at the left-hand end, The relays RAR and NAR control relays RAP and NA]? which may be employed for any appropriate purpose. The equipment at each end of the section includes a source of direct current, such as a battery, not shown, the terminals of which are designated B and C in the drawings.

The supply of energy to the relay CTM is controlled by a continuously operating code transmitter CT with the result that the contacts of the relay CTM are continuously actuated between their released and their picked-up positions at a rate determined by the code transmitter.

The polarity of the energy supplied from the battery 13 to the section rails is governed by contacts of a relay PC which may be controlled in any appropriate manner so that at times the relay contacts are released and at other times are picked up.

The transmitter relay IR is of the polar stick type and its contacts, when moved to either of their two positions, remain in that position until there is supplied to the relay winding energy of the polarity eifective to move the relay contacts to their other position.

As shown, contact ll! of the code transmitter CT is closed so energy is supplied to relay CTM and its contacts are picked up to interrupt the circuits of relays RAR and NAR and to establish the circuit of battery TB. As the circuits of relays RAR and NAR are interrupted, the contacts of these relays are released and interrupt the circuits of the relays RAP and NAP. As relay CTM is picked up, the positive terminal of the battery TB is connected over front contacts H and I2 of relay CTM to track'rail I, while the negative terminal of the battery is permanently connected to track rail 2. Accordingly, energy is supplied from the battery TB to the track rails and as the section is assumed to be vacant energy supplied to track rail I flows therefrom over left-hand or normal polar contact M of relay IR, over front contact l5 of relay IM, through the winding of relay TR from right to left, and over front contact iii of relay IM to track rail 2. The energy supplied to relay TR flows through the relay winding in the proper direction to pick up the relay contacts and they are picked up to establish the circuit to supply energy to the upper half of the primary winding of the decoding transformer DT, and to establish the circuit for supplying energy from the upper portion of a secondary winding of this transformer to relay H.

As the contacts of relay IR are in their lefthand or normal position energy is supplied over normal polar contact Hi to the winding of relay IM and its contacts are picked up to establish the circuit of the track relay TR, while contact IQ of relay IM connects one terminal of the winding of relay IR to a terminal of a secondary winding 20 of the transformer DT. The other terminal of the winding of relay IR is connected to the other terminal of the transformer secondary winding 20 and also to terminal 0 of the source.

The transformer DT and the relay IR are arranged so that the impulses of energy supplied from the transformer secondary winding to relay IR on picking up of the track relay TR are of the polarity effective to maintiain the contacts of relay IR in their normal position, and on reto relay TR is cut off and the contacts of relay TR release with the result that the supply of energy to the upper portion of the primary winding of transformer DT is cut off and a circuit is established to supply energy to the lower portion of this winding. As a result of the changes in energization of the transformer primary winding an impulse of energy is induced in each of the transformer secondary windings. The energy induced in one of the transformer secondary windings is rectified by a contact of the relay TR, as explained in Letters Patent of the United States No. 2,237,788 issued April 8, 1941 to myself and Leslie R, Allison, and is supplied to relay H, which is slow enough in releasing to remain picked up in the intervals between the supply of impulses of energy thereto.

The impulse of energy induced in secondary winding 20 of transformer DT is supplied over front contact IQ of relay IM to the winding of relay IR and is of such polarity as to move the contacts of relay IR to their right-hand or reverse position in which contact l4 interrupts the circuit of relay TR and establishes a circuit for supplying energy from battery IE to the track rails.

On movement of contact of relay IR to its reverse position at a time when the contacts of relay PC are picked up, as shown in the drawing, the battery 13 is connected across the track rails over the circuit which is traced from track rail 2 through a resistor 2| and over front contact 22 of relay PC to the positive terminal of battery IB, and from the negative terminal of this battery over front contact 23 of relay PC and reverse polar contact of relay IR to track rail I.

The energy supplied from battery IB at this time flows over track rail 2, through the winding of relay NAR from right to left, over back contacts H and 12 of relay CTM in series, and through the winding of relay RAR from right to left to track rail l. The energy supplied from battery IB at this time, therefore, is of the polarity effective to pick up the contact of relay NAR, but ineffective to pick up relay RAR. Accordingly, contact 25 of relay NAR picks up and establishes a circuit for suppling energy to relay NAP.

In addition, on movement of the contacts of relay IR to their reverse position, contact l8 interrupts the circuit of the repeater relay IM, and after a short time interval the contacts of relay IM release with the result that its contacts I5 and I6 additionally interrupt the circuit of relay TR, while contact I 9 of relay IM disconnects the winding of relay IR from the transformer secondary winding 20 and establishes a circuit to supply from the local source to the winding of relay IR energy of the polarity effective to move the relay contacts to their normal position. When the contacts of relay IR return to their normal position, contact l8 establishes the circuit for supplying energy to the winding of relay IM and contact I4 of relay IR interrupts the circuit of the batleading to a terminal of the winding of the relay TR. 7

The relay IM is snubbed by a resistor so thatposition until after the contacts of relay IR have been in their reverse position for a short time interval. When the contacts of relay IR are in their reverse position, energy is supplied from battery 18 to the section rails so the delay in the release of relay IM insures that the relay IR will establish the circuit of the battery IB long enough to cause the energy impulse supplied to the track rails to be of sufficient duration to pick up the relay 'NAR or RAR.

On release of relay IM energy is supplied to the winding of relay IR and moves the contacts of relay IR from their right-hand or reverse position to their left-hand or normal position with the result that contact I4 of relay IR interrupts the supply of energy from battery IE to the track rails. In addition, on this movement of the contacts of relay IR to their normal position contact I8 establishes the circuit of the relay IM and its contacts pick up with the result that contact l9 interrupts the circuit for supplying energy from the battery to the winding of relay IR and connects this relay to the secondary winding of the transformer DT. When the contacts of relay IM pick up, its contacts I5 and I6 complete the circuit for connecting the relay TR across the track rails.

On interruption of the supply of energy from the battery IE to the track rails, the relay NAR releases and interrupts the circuit of the relay NAP. However, the relay NAP is of a type the contacts of which are slow in releasing so that the relay contacts remain picked up during the released periods of relay NAR as long as the relay NAR is responding to coded energy.

Soon after release of relay NAR the contact I of code transmitter CT is moved to its closed position and the contacts of relay CTM pick up to interrupt the circuits of the relays NAR and RAR and to establish the circuit traced above for supplying energy from battery TB to the track rails. This energy feeds over the track rails and over normal polar contact M of relay IR and front contacts l5 and I6 of relay IM to the winding of relay TR and picks up the relay contacts.

When the contacts of relay TR pick up, the supply of energy to the lower half of the primary winding of transformer DT is interrupted and the supply of energy to the upper half of this winding is reestablished so an impulse of energy is induced in each of the transformer secondary windings. The energy induced in one of the transformer secondary windings is rectified by a contact of the track relay and is supplied to the winding of relay H to keep the relay contacts picked up.

The energy induced in secondary winding 20 of transformer DT upon picking up of the contacts of the relay TR is supplied over front contact I9 of relay IM to the winding of relay IR. This energy impulse is of the polarity effective to maintain the contacts of relay IR in their normal position so no movement of the contacts of relay IR occurs at this time.

On sub-sequent operation of the code transmitter CT to interrupt the circuit of relay CTM relay TR is PC the resistor 2| its contacts release and interrupt the circuit of the battery TB and connect the relays NAR and RAR across the track rails. As a result of interruption of the supply of energy from battery TB to the track rails, the relay TR releases and an impulse of energy is supplied from the transformer DT tothe relay IR and is of the polarity eil'ective to move thecontacts of relay IR to their reverse position with the result that energy is supplied from battery IB to the section rails while relay IM releases to establish the circuit for supplying energy to relay IR to restore its contacts to their normal position.

As long as the section is vacant the equipment operates as described above. The relay CTM is operated by the code transmitter CT and alternately connects the battery TB and the relays NAR and RAR across the track rails. The energy supplied from Battery TB over the section rails picks up the contacts of the relay TR, while release of the relay TR causes relays IR and IM to operate as explained above to supply an lmpulseof energy from the battery IB over the track rails to pick up relay NAR, and to then reconnect the relay TR across the track rails.

As a result of operation of relay TR the relay H is maintained picked up by energy supplied through the transformer DT, while the relay NAP is maintained picked up by energy supplied thereto during the picked-up periods of the relay NAR.

The equipment operates .in a similar manner when relay PC is released. At this time the picked up byenergy supplied over the track rails from battery TB while on release of relay TR the contacts of relay IR are moved to their reverse position so that energy is supplied to the track rails from battery IB over the circuit which is traced from track rail I over reverse polar contact H of relay IR and back contact 22 of relay PC to the positive terminal of the battery IB, and from track rail 2 over front contact I6 of relay IM, through the winding of relay TR from left to right, over front contact l5 of relay IM, and over back contact 23 of relay PC to the negative terminal of the battery IB. At this time the energy supplied from battery IE to the track rails is supplied over a circuit which includes in series therewith the winding of the relay TR, but the energy supplied through the relay winding is of the wrong polarity to pick up the relay contacts so they are certain to remain released.

The winding of the relay TR is of relatively low resistance so this winding has relatively little efiect on the value of the energy supplied from the battery IE to the track rails, but in order to render operation of the track circuit uniform in both positions of the contacts of the relay is included in the circuit over which energy is supplied from the battery IE to the track rails when the relay PC is picked up. The resistor 2| is selected so as to have resistance substantially equal to that of the winding of relay TR so that the energy supplied from the battery 13 to the track rails is of substantially the same value in both positions of the contacts of relay PC.

The circuit traced above for supplying energy from battery IE to the track rails when relay PC is released is interrupted when relay IM releases and opens its front contacts l5 and Hi. In this respect this circuit differs from that over which energy is supplied from battery IB when relay PC is picked up since when relay PC is picked up the circuit of the battery IB is not interrupted until the contacts of relay IR are moved away from their reverse position, whicn occurs as a result of the supply of energy to the relay winding over the circuit established by back contact I9 of relay IM. Accordingly, the impulses of energy supplied from battery 13 to the track rails when relay PC is released are slightly shorter than those supplied when relay PC is picked up but this difference is so small that it has no significance.

'As explained above, when relay PC is released and contact Id of relay IR establishes the circuit of the battery IB, the positive terminal of the battery IB is connected to track rail l. Accordingly, energy supplied from the battery 13 at this time flows from track rail I through the winding of relay RAR from left to right, over back contacts l2 and H of relay CTM, and through the winding of relay NAR from left to right to track rail 2, The direction of flow of energy through the windings of relays RAR and NAR at this time is such, therefore, as to pick up the contacts of relay RAR but not of relay NAR. Accordingly, the contact of relay RAR establishes the circuit of the relay RAP and. its contacts. are picked up, while the relay NAR does not establish the circuit of relay NAP and its contacts remain released.

If there is a change in trafiic conditions so that relay PC picks up, the circuit first described for supplying energy of the other polarity from battery IE to the track rails is established. On this change in the polarity of the energy supplied to the track rails the relay RAR remains released and the relay RAP releases, while the relay NAR responds to the energy supplied over the track rails and establishes the circuit of relay NAP so that its contacts pick up.

When a train is present in the section, the shunting efiect of the wheels and axles of the vehicles comprising the train prevents energy supplied from battery TB from reaching the relay TR and it remains released and does not cause energy to be supplied through the transformer DT to the relays H and IR. Accordingly, relay H releases and remains released, while relay IR is not operated to supply impulses of energy from the battery IB to the track rails and the relays RAR and NAR remain released and the relays RAP and NAP both remain released.

The equipment at the left-hand end of the section is arranged so that irrespective of the position of the contacts of the relay PC, the relay TR will not be picked up by energy supplied from the battery IB in the event movable contact M of relay IR simultaneously engages the associated normal and reverse stationary contacts.

When relay PC is picked up, the positive terminal of the battery IB is connected over front contact 22 ofrelay PC to the wire leading to track rail 2, while front contact l6 of relay IM establishes connection from this wire to the lefthand terminal of the winding of relay TR. At this time the negative terminal of the battery IB is connected over front contact 23 of relay PC to the right-hand or reverse stationary contact associated with movable contact M of relay IR. If for any reason contact [4 of relay IR simultaneously engages both of the associated stationary contacts, the negative terminal of the battery 13 will be connected through contact I! of relay IR and over front contact l5 of relay IM to the right-hand terminal of the winding of relay TR. Since under these conditions connection is established from both terminals of the battery IE to the terminals of the winding of relay TR energy will be supplied from the battery IB through the winding of relay TR, However, the contacts of the relay TR will not be picked up by the energy supplied from battery IE to the relay winding because the circuit connections between the battery and the relay are'such that the energy supplied to the relay winding is of the wrong polarity to pick up the relay contacts. Accordingly, they remain released and will not cause energy to be supplied through the transformer DT to the relay H.

When the relay PC is released, the negative terminal of the battery IB is connected over back contact 23 of relay PC and front contact l5 of relay IM to the right-hand terminal of the winding of relay TR, while the positive terminal of the battery 13 is connected over back contact 22 of relay PC to the right-hand or reverse stationary contact associated with movable contact [4 of the relay 1R. If for any reason movable contact 14 of relay IR simultaneously engages both of the associated stationary contacts, the positive terminal of the battery IB will be connected over back contact 22 of relay PC and through contact I4 of relay IR to the wire which is connected over back contact 23 of the relay PC to the negative terminal of the battery IB. Accordingly, the battery IB is short circuited, and as a result energy will flow between the terminals of the battery through this short circuit connection and will not flow through the winding of the relay TR. The contacts of the relay TR, therefore, remain released and do not cause energy to be supplied through the transformer DT to the relay H. i

From the foregoing it will be seen that the circuits of the relay TR and of the battery IB are arranged so that if for any reason movable contact I4 of relay IR simultaneously engages both of the associated stationary contacts, the contacts of the relay TR will not be picked up by energy supplied from the battery IB. Accordingly, there is no possibility that relay H will be improperly picked up as a result of operation of relay TR by energy supplied from the battery 13.

The equipment at the left-hand end of the track section is also arranged so that the relay TR will not be operated by energy inductively discharged from the track circuit on interruption of the supply of energy from battery IE to the track rails.

Because of the inductance of the track circuit an impulse of energy is induced therein on interruption of the flow of energy in the track rails.

The impulse of energy induced in the track circuit at this time flows in the same direction as the energy which was being supplied to the track rails. Since energy of both polarities is supplied from the battery D3 to the track rails, it follows that the impulses of energy induced in the track circuit on interruption of the supply of energy from the battery IB are of one polarity at times and are of the other polarity at other times and that the relay TR might be operated by the impulses of one polarity if these impulses of energy are permitted to reach the winding of the relay TR. The equipment at the left-hand end of the track section is arranged to insure that after each interruption of the circuit of the battery 13 a time interval long enough to permit energy induced in the track circuit to be dissipated, or to be reduced n to a low ineffective value, will elapse before the relay TR is connected with the track rails. This eliminates the possibility of improper operation of the relay 'I'R by energy inductively discharged from the track circuit.

As explained above, on release of relay IR, an impulse of energy is supplied from the secondary winding 20 of the transformer DT to the relay IR and moves the relay contacts to their reverse position in which contact l4 interrupts the circuit for connecting relay TR across the track rails and establishes a circuit for'supplying from battery IE to the track rails energy of one polarity or the other dependlng'on the position of the contacts of the relay PC. In addition, on this movement of the contacts of relay IR to their reverse position contact iii of relay IR interrupts thecircuit of relay IM and after a short time interval its contacts release to interrupt the circuit of the winding of relay TR and to establish the circuit for supplying energy to the winding of relay IR to move the relay contacts to their normal position.

on this movement of the contacts of relay IR, contact l4 interrupts the supply of energy from the battery IE to the track rails, if it was not interrupted on opening of the front contacts I 5 and I6 of relay IM. In addition, on this movement of the contacts of relay IR to their normal position contact 18 establishes the circuit of the relay IM and its contacts pick up so that contacts l5 and I6 complete the circuit for connecting relay TR across the track rails, while contact l9 transfers the circuit of relay IR from the local source of energy to the secondar winding 20 of transformer DT.

Although the relay IM is of a type the contacts of which are quick to respond, they will not respond' instantaneously upon the supply of energy to the relay winding so there is certain to be a short time interval from the instant at which contact H! of relay IR establishes the circuit of relay IM and the instant at which the front contacts of relay IM are closed. Accordingly, there is certain to be a short time interval between the instant at which contact 14 of relay IR disengages its right-hand or reverse contact, at which time the supply of energy from the battery IE to the track rails is interrupted if it was not interrupted shortly before on opening of front contacts l5 and is of relay IM, and the instant at which front contacts l5 and 1'6 of relay IM are closed to complete the circuit for connecting the winding of relay TR across the track rails. This time interval is long enough to per mit the impulse of energy induced in the track circuit on interruption of the circuit of the battery IE to be dissipated or to be reduced to a low ineffective value before the relay TR is connected across the track rails. This time interval, therefore, insures that relay TR will not be improperly operated by energy inductivelydischarged from the track circuit. Since this time interval is determined by the pick-up time of relay IM it is certain to be present and will not be eliminated or reduced in length to an ineffective value by changes in operating conditions. Hence the time interval which is relied upon to prevent operation of relay TR; by energy inductively discharged from the track circuit is certain to be provided after each interruption of the circuit of the battery IB.

In addition. it will be seen that on movement of the contacts of the relay IR to their reverse position they remain in that position until relay 10 IM releases to establish the circuit for supplying energy to the relay IR to restore its contacts .to their normal position. When relay IM releases to establish the circuit for relay IR, it also interrupts the circuit of the relay TR and thus insures that the circuit of the relay TR is interrupted at the time relay IR operates to interrupt the circuit of the battery 1B. This insures that if relay IR operates to interrupt the circuit of the battery IB so that an impulse of energy is inductively discharged from the track circuit, the circuit of the relay TR will be interrupted by the contacts of the relay IM to thereby make certain that the energy inductively discharged from the track circuit will not be supplied to relay TR. If for any reason the relay IM should fail to release, and therefore should not interrupt the circuit of the relay TR, the contacts of relay IR will not be moved away from their reverse position to interrupt the circult of the battery. Under these conditions failure of relay IM to interrupt the circuit of relay TR cannot result in improper supply of energy to relay TR since there is no impulse of energy inductively discharged from the track circuit.

Modification shown in Fig. 1A

In Fig. 1A of the drawings there is shown a modified circuit arrangement for controlling the relay IR and is adapted for use in situations where the signaling apparatus is arranged as shown in Letters Patent of the United States No. 2,282,083 issued to me on May 5, 1942.

As shown, a repeater relay TM is provided for the relay TR and is energized over a front contact of the relay TR. The left-hand terminal of the winding of relay IR is connected to the mid point of a resistor 21 which is connected between terminals B and C of the local source of energy.

On release of the contacts of relay TR contact 28 interrupts the circuit of relay TM, but the relay TM is slightly slow in releasing and remains picked up for a shorttime after release of relay TR. In the interval after release of relay TR and before release of relay TM energy is supplied to relay IR over the circuit which is traced from terminal B of the source over back contact 28 of relay TR, front contact 29 of relay TM, front contact 19 of relay IM, through the winding of relay IR from right to left, and through the lower portion of the resistor 21 to terminal 0 of the source. The energy supplied to relay IR moves the relay contacts to their right-hand or reverse position in which contact I8 interrupts the circuit of relay IM and its contacts release.

After release of relay IM energy is supplied to the relay IR over the circuit which is traced from terminal B of the local source of current through the upper portion of the resistor 21, through the winding of relay IR from left to right and over back contact IQ of relay IM to terminal C of the source. The energy supplied to relay IR at this time moves the relay contacts to their normal position in which contact 13 establishes the circuit of relay IM and its con- I the relay TR the relay TM picks up but at this time contact 28 of relay TR interrupts the circuit I of relay IR and its contacts remain in their normal position. On release of the relay TR energy is again supplied to relay IR to move its contacts to their reverse position and the cycle of operation described above is repeated.

The relays IR and IM cooperate as explained in connection with Fig. 1 to control the circuits of the relay TR and of the battery 13 and a detailed description of these circuits is unnecessary.

Similarly, the relay TM has movable contacts in addition to contact 29, and these contacts are employed to control code detecting means, not shown.

Modification shown in Fig. 2

In some situations the operating characteristics of the code following relay employed as the relay TR are such that the relay will not respond to energy of the value of the impulses inductively discharged from the track circuit on interruption of the supply of energy from battery 13. Where this is the situation it is unnecessary to provide the time interval between interruption of the circuit of the battery IBand establishment of the circuit of the relay TR so the relay IM, which is employed to provide this time interval, may be omitted. In this situation, however, it is desirable to retain the circuit arrangement which prevents operation of relay TR by energy from the battery 13 in the event the movable contact of relay IR simultaneously engages both of the associated stationary contacts.

In addition, in some situations, in order to operate track circuits of the maximum length, it is desired to arrange the equipment so that the energy supplied from battery 3 to the track rails is not reduced in value because the energy supplied from the battery is supplied through the winding of relayTR or through a resistance of similar value.

In Fig. 2 of the drawings there is shown anparatus which is arranged as outlined above. The modification shown in Fig. 2 is similar to that shown in Fig. 1, but differs therefrom in that the relay IM is not employed, while the relay IR is of the polar biased neutral type and has contacts which are biased to their released position from which they are moved to their picked-up position when and only when energy of a particular polarity is supplied to the relay winding.

The-modification shown in Fig. 2 is shown in the condition which it assumes when the relay PC is picked up and when the contacts of the relay TR are picked up by energy supplied from the track rails over the circuit which includes back contact M of relay IR. At the end of the energy impulse supplied over the track rails the contacts of the relay TR release with the result that an impulse of energy is induced in each of the secondary windings of the transformer DT. The energy impulse induced in the secondary winding 20 is supplied to the winding of relay IR. The equipment is arranged so. that the impulse of energy induced in secondary winding 20 on release of the contacts of relay TR is of the polarity effective to pick up the contacts of the relay IR and will maintain them picked up for a short time interval.

When the contacts of relay IR pick up and relay PC is picked up, as shown in the drawings, the circuit for connecting relay TR across the 12 track rails is interrupted and the battery I13 connected across the track rails. At this time the positive terminal of the battery IB is connected over front contact 22 of relay PC to track rail 2, while the negative terminal of the battery IB is connected over front contact 23 of relay PC and over front contact I! of relay IR to track rail I so that energy is supplied from the battery 13 to the track rails. Except for the customary limiting resistor, the circuit over which energy is supplied from the battery 13 to the track rails does not include any resistance other than that of the wires forming the circuit so the energy supplied to the track rails is of the maximum voltage and will operate a track circuit of maximum length.

On release of the relay IR its contact l4 interrupts the circuit of the battery IB and connects the relay TR across the track rails. On the supply of another impulse of energy over the track rails the contacts of the relay TR pick up with the result that another impulse of energy is induced in each of the transformer secondary windings. The impulse of energy induced in winding 20 is supplied therefrom to the winding of relay IR, but is of the wrong polarity to pick up the contacts of relay IR so contact l4 remains released and maintains the circuit of the relay TR.

On interruption of the supply of energy over the track rails the relay TR releases and the cycle of operation described above is repeated.

The equipment operates in a similar manner when relay PC is released. At these times the negative terminal of the battery IB is connected over back contact 23 of relay PC to the righthand terminal of the winding of relay TR, while the positive terminal of the battery IB is connected over back contact 22 of relay PC to the wire leading into front contact M of relay IR. When the contacts of relay IR pick up, the positive terminal of the battery IB is connected over front contact ll of relay IR to track rail I, while front contact 30 of relay IR establishes a conneotion between the terminals of the winding of relay TR so that the negative terminal of the battery 13 is connected to track rail 2 over the circuit established by front contact 30 of relay IR as well as through the winding of relay TR. Accordingly, when relay IR picks up at a time when the contacts of relay PC are released, the battery IB is connected across the track rails so as to supply to the track rails energy of the polarity such that track rail I is positive with respect to track rail 2.

As contact 30 of relay IR, when picked up, establishes a circuit shunting the winding of relay TR, the resistance represented by the winding of relay TR is removed from the circuit over which energy is supplied from the battery IE to the track rails and the impulses of energy supplied to the track rails are of the maximum value and will operate a track circuit of maximum length.

On release of the contacts of the relay IR the circuit for supplying energy from battery 13 and the circuit shunting the winding of relay TR are interrupted, while the circuit for connecting the winding of relay TR across the track rails is reestablished. 1

The modification shown in Fig. 2 is arranged so that relay TR will not be picked up by energy supplied thereto from battery B if for any reason the contacts of relay IR are defective or are out of adjustment.

winding is of the wrong When the contacts of relay PC are picked up, the positive terminal of the battery IB is connected over front contact 22 of relay PC to the left-hand terminal of the winding of relay TR. If at this time movable contact [4 of relay IR should simultaneously engage both of the associated stationary contacts, a connection will be established from the negative terminal of the battery IB over front contact 23 of relay PC and through contact H of relay IR to the right-hand terminal of the winding of the relay TR. Accordingly, if under these conditions energy is supplied from battery IE to the winding of relay TR, it will flow through the relay winding in the wrong direction to pick up the relay contacts so there is no possibility that the contacts of relay TR will be picked up by this energy.

When the contacts of relay PC are released, the negative terminal of the battery IB is connected over back contact 23 of relay PC to the wire leading to back contact M of relay IR and also to the right-hand terminal of the winding of relay TR. If at this time movable contact M of relay IR simultaneously engages both of the associated stationary contacts, the positive terminal of the battery 13 will be connected over back contact 22 of relay PC and through contact M of relay IR to the wire which is connected over back contact 23 of relay PC to the negative terminal of the battery IB. Accordingly, the battery IB is shortcircuited and energy therefrom will flow through the short-circuit connection instead of through the winding of relay TR and the contacts of relay TR will not be picked up by energy supplied from battery 13 at this time.

As explained above, when relay IR picks up, its contact 3!] establishes a circuit shunting the winding of relay TR and energy is supplied from battery 13 to the track rails through this circuit when the relay PC is released. Atthis time the battery IB is also connected across the track rails through the winding of relay TR and if for any reason the circuit governed by contact 30 of relay IR is not established, energy from the battery IE will be supplied through the winding of relay TR. However, under these conditions, the negative terminal of the battery IB is connected to the right-hand terminal of the winding of relay TR s energy supplied through the relay polarity to pick up the relay contacts and they are certain to remain released. The resistance represented by the winding of relay TR will reduce the value of the impulses of energy supplied from battery 13 to the track rails and may make them inadequate to operate the relay at the opposite end of the track section, but this will be a safe failure and cannot create a hazardous condition.

When the contacts of relay PC are picked up. the circuitfor supplying energy from battery 13 to the track rails is independent of the winding of relay TR and failure of contact 30 to establish the circuit shunting the winding of relay TR cannot result in improper supply of energy to the winding of relay TR.

If for any reason contact 30 of relay IR is closed when it should be open, it will establish the circuit shunting the winding of relay TR and will prevent response of relay TR to energy supplied over the track rails. relay H will remain released and will not be improperly picked up. Release of relay H may delay trafiic in the track section but will not create a hazardous condition. 7

From the foregoing it will be seen that failure Under these conditions,

of contact 3|] to establish or to interrupt the cir- Modification shown in Fig. 3

In Fig. 3 of the drawings there is shown a modifled circuit arrangement which is adapted for use where the supply of impulses of feed-back energy to the rails of a track section is governed by means of the type shown in my Letters Patent of the United States No. 2,021,944, granted November 26, 1935. Where this means for supplying impulses of feed-back energy to the section rails is employed, a movable contact on the track relay TR, when in one position, establishes a circuit to connect the winding of the track relay across the track rails, and when in its other position establishes a circuit for connecting the battery across the track rails. The circuits provided by this modification are arranged to insur that if this movable contact of the track relay simultaneously engages both of the associated stationary'contacts, energy from the battery will not pick up the contacts of the track relay.

Where this method of supplying impulses of feed-back energy to the track rails is employed, a repeater relay TP is provided for the track relay TR and has contacts which control the circuit of the .track relay winding and of the battery. The circuits provided by this modification also opcrate to prevent improper supply of energy from the battery to the track relay in the event the contacts of the repeater relay TP are defective.

The equipment is shown in the condition which it assumes when the contacts of the track relay TR are picked up. At this time the winding of the relay TR is connected across the track rails over its stick circuit which is traced from track ra'l I over front contact 32 of relay TR, and through the winding of relay TR from right to left to track rail 2.

As relay TR is picked up, its contact 33 establishes the circuit of the repeater relay TP and its contacts are picked up so that contact 34 interrupts the pick-up circuit of relay TR and contact 35 in the circuits leading from battery IB is closed.

At the end of the impulse of energy supplied over the track rails the relay TR releases and i s contact 33 interrupts the circuit of the relay TP and short-circuits the relay winding. Because of this short-circuiting of the winding of relay TP and because of the resistor snub connected across the terminals of the relay winding, the relay contacts are slightly slow in releasing and remain picked up for a short time subsequent to release of relay TR.

On release of relay TR its contact 32 interrupts the stick circuit for relay TR and establishes a circuit over which energy is supplied from battery IE to the track rails as long as relay TP is picked up. This energy is of one polarity or the other according as the contacts of relay PC are picked up or are released. After a short time interval the contacs of relay TP release and contact 35 interrupts the circuit of the battery IB andthus cuts off the supply of energy from this battery to the track rails, while contact 34 connects track rail I to the right-hand terminal of the winding of relay TR to thereby establish the pick-up circuit for relay TR.

On the subsequent supply of an impulse of energy over the track rails to the relay TR its contacts pick up and contact 32 establishes the relay stick circuit before contact 34 of relay TP picks 15 up to interrupt the pick-up circuit for relay TR. Accordingly, when relay TR picks up, it remains picked up as long .as energy is'supplied over the track rails. v

n continued supply of coded energy over the track rails the equipment operates as described above. The relay TP picks up when the relay TR picks up. and on release of relay TR the battery IB is connected across the track rails as long as relay TP remains picked up.

The relay TR has movable contacts in addition to contacts 32 and 33 and these may be employed to control code detecting means of any wellknown type.

When relay PC is picked up, the negative terminal of the battery IB is connected over front contact 23 of relay PC and through the winding of relay TR to the track rail 2. At this time the positive terminal of the battery IB is connected over front contact 22 of relay PC to track rail I over the circuit governed by front contact 35 of relay TP and back contact 32 of relay TR. Accordingly', when relay PC is picked up, the energy supplied from battery IB to the track rails is of the polarity in which track rail l is positive with respect to track rail 2. At this time, since the negative terminal of the battery 13 is connected to track rail 2 through the winding of relay TR, the energy supplied from the battery 13 to the track rails flows through the winding of the relay TR. However, this energyis of the wrong polarity to pick up the contacts of the relay TR and they are certain to remain released.

11, while relay PC and contact 35 of relay TP are picked up, contact 32 of relay TR engages both of the associated stationary contacts, the battery IE will be short-circuited but no circuit will be established which will cause energy to be supplied from the battery IE to the winding of relay TR which will pick up the contacts of the relay TR.

Likewise, if, while relay PC is picked up, the contacts of relay TP are defective or are out of adjustment so that back contacts 34 of relay TP is closed at a time when front contact 35 of relay TP and back contact 32 of relay TR are closed, the battery IE will be short-circuited, and energy will not be supplied from the battery to the relay TR which will pick up the contacts of the relay TR.

When the contacts of the relay PC are released, the positive terminal of the battery 1B is connected over back contact 22 of relay PC and through resistor 2| to track rail 2 and also to the left-hand terminal of the winding of relay TR. When relay TR is released and relay TR is picked up, the negative terminal of the battery IB is connected over back contact 23 of relay PC, front contact 35 of relay TP, and back contact 32 of relay TR to track rail I. Accordingly, when relay PC is released, the energy supplied from battery IE to the track rails is of the polarity in which rail 2 is'positive with respect to rail I, while the circuit over which this energy is supplied from the battery IE to the rails is independent of the winding of the relay TR. The resistor 2|. is included in this circuit and has substantially the same resistance as the winding of the relay TR so the impulses of energy supplied to the track rails when relay PC is released are of substantially the same value as the impulses supplied when relay PC is picked up.

If, while relay .PC is released and relay TP is picked up, contact 32 of relay TR simultaneously engages both of the associated stationary contacts, energy will be supplied from battery 13 to the winding of relay TR over the circuit which is traced from the positive terminal of the battery winding of relay TR at this time fiows through the relay winding from left to right, it is ineffective to pick up the relay contacts so they are certain to remain released.

If, while relay PC is released, the contacts of relay TP are defective or are out of adjustment so that back contact 34 and front contact 35 are closed at a time when relay TR is released, energy will be supplied from the battery 13 to the relay TR over the circuit which is traced from the positive terminal of the battery IB over back contact 22 of relay PC, through resistor 2|, through the winding of the relay TR from left to right, over back contact 34 of relay TP, back contact 32 of relay TR, front contact 35 of relay TP, and back winding from left to right, it is ineffective to pick a biased to a released position and movable thereup the relay contacts and the relay is certain to remain released.

As the circuits for supplying energy from the battery IE to the track rails are arranged so that energy effective to pick up the contacts of relay TR will not be supplied from the battery 13 to the relay winding, there is no danger that the code detecting means governed by relay TR will be improperly energized because of operation of relay TR by energy supplied from the battery IB.

Although I have herein shown and described only three forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a coded signaling system, in combination, a first and a second conductor over which impulses of energy of a selected polarity are at times supplied, a code following relay having a contact from to a picked-up position when and only when energy fiows through the relay winding in a selected direction, a source of direct current, a pole changing relay having contacts which at times occupy a first position and at other times occupy a second position, means for connecting said first conductor to the first terminal of said code following relay and also to the second terminal of said source when the contacts of said pole changing relay are in their first position, means for connecting said second conductor to a movable contact which is recurrently operated between a first position in which it engages a first stationary contact and a second position in which it engages a second stationary contact, means for connecting the second terminal of the winding of said code following relay to said first stationary contact and also to the first terminal of said source when the contacts of said pole changing relay are in their second position, means for connecting said second stationary contact to the first or the second terminal of said source according as the contacts of said pole changing relay are in their first or their second position, the connections with said source being arranged so that energy supplied therefrom to said conductors when the contacts of said pole changing relay are in their second positionfiows through the winding of said code following relayin the reverse of said selected direction, the connections between said conductors and the terminals of the winding of said code following relay being arranged so that when the winding of said relay is connected across said conductors energy of said selected polarity supplied over said conductors flows through the winding of said relay in said selected direction.

2. In a coded signaling system, in combination, a first and a second conductor over which at times are supplied impulses of energy of the polarity in which the second conductor is positive with respect to the first conductor, a code following relay having a contact which is moved from a second to a first position when and only when energy flows through the relay winding from the second to the first-terminal thereof, a source of direct current, a pole changing relay having contacts which at times occupy a first position and at other times occupy a second position, a movable contact which isrecurrently operated between a first and a second position, said movable contact being effective when in its first position to establish a circuit for connecting the winding of said code following relay across said conductors with the first terminal of said winding connected to said first conductor,said movable contact being effective when in its second position and the contacts of said pole changing relay are in their first position to establish a circuit independent of the winding of said code following relay for connecting said source of direct current across said conductors with the positive terminal thereof connected to said first conductor, said movable contact being effective when in its second position and the contacts of said pole changing relay are in their second position to establish a circuit including in series therewith the winding of said code following relay for connecting said source ofcurrent across said conductors with the positive terminal of said source connected to'said second conductor.

3. In a coded track circuit signaling system, in combination, a section of railway track having a first and a second track rail, a first transmitting relay at the first end of said section having contacts which are recurrently operated between a first position in which they connect a first source of direct current across said track rails with the positive terminal of said source connected to said first track rail, and a second position in which they connect a first and a second code following relay across said track rails so that the first code following relay responds only to energy of one polarity supplied over the track rails and so that the second code following relay responds only to energy of the other polarity supplied over the track rails, a second transmitting relay at the second end of said section having contacts which are recurrently operated between a first and a second position, a third code following relay located at the second end of said section and having a normally released contact which is picked up when and only when energy flows through the relay winding from the second to the first terminal thereof, circuit means effective only when the contacts of said second transmitting relay are in their first position for connecting the winding of said third code following relay across said track rails with the second terminal of the winding of said third code following relay connected to said first track rail, a second source of direct current, circuit means effective at times when the contacts of said second transmitting relay are in their second position to connect said second source of 'direct current across said track rails independently of the winding of said third code following relay with the positive terminal of said source connected to said second track rail, and circuit means effective at other times when the contacts of said second transmitting relay are in their second position for connecting said second source of direct'current across said track rails in series with the winding of said third code following relay with the positive terminal of said second source of directcurrent connected to said first track rail.

4. In a coded track circuit signaling system, in combination, a section of railway track having a firstand a second track rail, a first transmitting relay at the first end of said section having contacts which are recurrently operated between a first positionin which they connect a first source of direct current across said track' rails with the positive terminal of said source connected to said first track rail, and a second position ing of said repeater relay when the contacts of said second transmitting relay are in their first position, a third code following relay located at the second end of said section and having a normally released contact which is picked up when and only when energy flows through the relay winding from the second to the first terminal thereof, circuit means effective only when the contacts of said second transmitter relay are in their first position and the contacts of said repeater relay are picked up for connecting the winding of said third code following relay across said track rails with the second terminal of the winding of said third code following relay connected to said first track rail, a second source of direct current, circuit means effective at times when the contacts of said second transmitting relay are in their second position to connect said second source of direct current across said track rails independently of the winding of said third code following relay with the positive terminal of said source connected to said second track rail, and circuit means effective at other times when the contacts of said second transmitting relay are in their second position for connecting said second source of direct current across said track rails with the positive terminal of said source connected to said first track rail.

5. In a coded signaling system, in combination. a pair of conductors, a code following relay having a contact biased to a first position and movable therefrom to a second position when and only when energy flows through the relay winding in a selected direction, a source of direct current, a pole changing relay having contacts which at times occupy a first position and at other times} occupy a second position, a transmitter relay having contacts which are recurrently operated between a first position in which they establish a circuit for connecting the winding of said code following relay across said conductors and a second position in which they establish a first supply circuit including first position contacts of said pole changing relay for connecting said source of direct current across said conductors independently of the'winding of said code following relay so as to supply energy of one polarity to said conductors or in which they establish a second supply circuit including second position contacts of said pole changing relay for connecting said source of direct current across said conductors through the winding of said code following relay so as to cause energy to fiow therethrough in the reverseof said selected direction and to cause to be supplied to said conductors energy the polarity of which is the reverse of that supplied over said first supply circuit.

6. In a coded signaling system, in combination, a first and a second conductor, a code following relay having a contact biased to a first position and movable therefrom to a second position when and only when energy fiows through the relay winding in a selected direction, the first terminal of the winding of said relay being connected to said first conductor, a source of direct current having a first and a second terminal, a pole changing relay having contacts whichat times occupy a first position and at other times occupy a second positon, and a transmitter relay having a contact which is recurrently operated between a first position in which it connects said second conductor to the second terminal of the winding of said code following relay and a second position in which it connects said second conductor to the first or the second terminal of said source of direct current according as the contacts of said pole changing relay are in their first or their second position, the contacts of said pole changing relay being effective when in their first position to connect the second terminal of said source of direct current to said first conductor and being effective when in their second position to connect the first terminal of said source of direct current to the second terminal of the winding of said code following relay, the equipment being arranged so that when the contacts of said pole changing relay are in their second position the energy supplied from said source to said conductors fiows through the winding of said code following relay in the reverse of said selected direction.

7. In a coded signaling system, in combination, a first and a second conductor over which at times are supplied impulses of energy of the polarity in which the second conductor is positive with respect to the first conductor, a code following relay having a contact biasedto a released position and movable therefrom to a picked-up position when and only when energy fiows through the relay winding from the second to the first terminal thereof, a source of direct current, a pole changing relay having contacts which at times occupy a first position and at other times occupy a second position, and a transmitter relay having a contact which is recurrently operated between a first and a second position, said transmitter relay contact being effective when in its first position to establish a circuit for connecting the winding of said code following relay across said conductors with the first terminal of said winding connected to said first conductor, said transmitter relay contact being effective when in its second position and the contacts of said pole changing relay are in their first position to establish a circuit independent of the winding of said code following relay for connecting 'said source of direct current across said conductors with the .positive terminal thereof connected to said first conductor, said transmitter relay contact being effective when in its second position and the contacts of said pole changing relay are in their second position to establish a circuit including in series therewith the winding of said code following relay for connecting said source of direct current across said conductors with the positive terminal of said source connected to said second conductor.

8. In a coded signaling system, in combination, a first and a second conductor over which at times are supplied impulses of energy of the polarity in which the second conductor is positive with respect to the first conductor, a code following relay having a contact which is moved from a first to a second position when and only when energy flows through the relay winding from the second to the first terminal thereof, a source of direct current, a pole changing relay having contacts which at times occupy a first position and at other times occupy a second position, and a transmitter relay having a contact which is recircuit for connecting the winding of said code following relay across said conductors with the first terminal of said winding connected to said first conductor, said transmitter relay contact being effective when in its second position and the contacts of said pole changing relay are in their first position to establish a circuit independent of the winding of said code following relay for connecting said source of direct current across said conductors with the positive terminal thereof connected to said first conductor, said transmitter relay contact being effective when in its second position and the contacts of said pole changing relay are in their second position to establish a circuit including in series therewth the winding of said code following relay -for connecting said source of direct current across said conductors with the positive terminal of said source connected to said second conductor.

9. In a coded signaling system, in combination, a first and a second conductor over which at times are supplied impulses of energy of a selected polarity, a code following relay having the first terminal of its winding connected to said first conductor, a source of direct current, a pole changing relay having contacts which at times occupy a first position and at other times occupy a second position, a transmitter relay having a contact which is recurrently operated between a first and a second position, said transmitter relay contact being effective when inits first position to connect saidsecond conductor to the second terminal of the winding of said code following relay and being effective when in its second position to connect said second conductor to the first or the second terminal of said source of direct current according as the contacts of said pole changing relay are in their first or their second position, the contacts of said pole changing relay being effective when in their first position to connect the second terminal of said source of direct current to the first terminal of the winding of said code following relay and being anc or? efiective when in their second position to connect the first terminal of said source of direct current to the second terminal of the winding of said code following relay, said code following relay having a contact which is moved from a first to a second position when and only when there is supplied to the relay winding energy of the polarity of the energy impulses supplied thereto over said conductors, the connections between said source of direct current and said conductors being arranged so that when the contacts of said pole changing relay are in their second position the energy supplied from said source through the winding of said code following relay is of the wrong polarity to move the relay contact from its, first to its second position.

10. In a coded signaling system, in combination, a first and a second conductor over which at times are supplied impulses of energy of a selected polarity, a transmitting relay having a movable contact to which the second conductor is connected and which is recurrently operated between a position in which it engages a first stationary contact and a position in which is engages a second stationary contact, a code following-relay having the first terminal of its winding connected to said first conductor and having the second terminal of its winding connected to said first stationary contact, a source of direct current,,a pole changing relay having contacts which at times occupy a first position in which they connect the first terminal of said source of direct current to said second stationary contact and connect the second terminal of said source of direct current to said first conductor and at other times occupy a second position in which they connect the first terminal ofsaid source of direct 1 current to the second terminal of the winding of said code following relay and connect the second terminal of said source of direct current to said second stationary contact, saidvcode following relay having a contact which is moved from a first to a second position when and only when there is supplied to the relay winding energy of the polarity of the energy impulses supplied ther to over said conductors, the connections between said source of direct current and said conductors being arranged so that when the contacts of said pole changing relay are in their second position the energy supplied from said source through the winding of said code following relay is of the wrong polarity to move the relay contact from its first to its second position.

11. In a coded signaling system, in combination, a first and a second conductor over which at times are supplied impulses of energy of a selected polarity, a transmitting relay having a first movable contact to which said second conductor is connected and which is recurrently op- =erated between a first position in which it engages a first stationary contact and a second position in which it engages a second stationary contact, a code following relay having the first terminal of its winding connected to said first conductor and having the second terminal of its winding connected to saidfirst stationary contact, said transmitting relay having a second movable contact which is moved substantially in synchronism with said first movable contact andwhich when in its second position establishes a circuit between the terminals of the source of direct current to said second stationwhich is moved from a first to a second position when and only when there is supplied to the relay winding energy of the polarity of themergy impulses supplied theretoover said conductors, the connections between said source of direct current and said conductors being arranged so that when the contacts of said pole changing relay are in their second position the energy sup plied from said source through the winding of said code following relay is of the wrong polarity to move the relay contact from its first to its second position.

12. In a coded signaling system, in combination, a first and a second conductor over which at times are supplied impulses of energy of a selected polarity, a transmitter relay having a plurality of contacts which are movable between a first and a second position, one-of said transmitter relay movable contacts being effective according as it is in its first or second position to connect said second conductor to a first or a second stationary contact, a repeater relay having contacts biased to a released position from which they are moved to a picked-up position when the relay winding is energized, a circuit for supplying energy to the winding of said repeater relay when the contacts of said transmitter relay are in their first position, means for recurrently moving the contacts of said transmitting relay from their first to their second position, means efiective upon movement of the contacts of said repeater relay to their released position for moving the contacts of said transmitting relay from their second to their first position, a code following relay having the first terminal of its winding connected over one front contact of said repeater relay to said first conductor and having the second terminal of its winding connected over another front contact of said repeater relay to said first stationary contact, a source of direct current, a pole changing relay -having contacts which at times occupy a first position in which they connect the first terminal of said source of direct current to said second stationary contact and connect the second terminal of said source of direct current to said first conductor and at other times occupy a second position in which they connect the first terminal of said source of direct current to said first stationary contact and connect the second terminal of said source of direct current to said second stationary contact, said code following relay having a contact which is moved from a first to a second position when and only when there is supplied to the relay winding energy of the polarity of the energy impulses supplied thereto over said conductors, the connections between said source of direct current and said conductors being arranged so that when the contacts of said pole changing relay are in their second position the energy supplied from said source through the winding of said code following relay is of the wrong polarity to move the relay contact from its first to its second position.

13. In a coded signaling system, in combination, a transmitting relay having contacts which 23 are movable between a first and a second position, a repeater relay governed by said transmitting relay so that the contacts of said repeater relay are moved to a first or a second position according as the contacts of said transmitting relay occupy their first or their second position, means for recurrently moving the contacts of said transmitting relay from their first to their second position, means responsive to movement of the contacts of said repeater relay to their second position for moving the contacts of said transmitting relay from their second to their first position,

a source of direct current, a pole changing relay having contacts which at times occupy a first position and at other times occupy a second position, a pair of conductors over which impulses of energy of a selected polarity are at times supplied, a code following relay having a contact which is moved from a first to a second position when and only when energy flows through the relay winding in a selected direction, circuit means effective only when the contacts of both of said transmitting and repeater relays are in their first position to connect the winding of said code fol-- lowing relay across said conductors so that impulses of energy of said selected polarity supplied over said conductors flows through the winding of said code following relay in said selected direction, circuit means effective when the contacts of said transmitting relay are in their second position and the contacts of said pole changing relay are in their first position for connecting said source of direct current across said conductors independently of the winding of said code following relay so as to supply energy of said selected polarity to said conductors, and circuit means effective when the contacts of said transmitting and pole changing relays are in their second position and the contacts of said repeater relay are in their first position for connecting said source of direct current across said conductors in series with the winding of said code following relay so as to supply energy of the reverse of said selected polarity to said conductors and to cause energy to be supplied through the winding of said code following relay in the reverse of said selected direction.

14. In a coded signaling system, in combination, a transmitting relay having contacts which are movable between a first and a second position, a repeater relay governed by said transmitting relay so that the contacts of said repeater relay are moved to a first or a second position according as the contacts of said transmitting relay occupy their first or their second position, means operative when the contacts of said repeater relay are in their second position for moving the contacts of said transmitting relay from their second to their first position, a, source of direct current, a pole changing relay having contacts which at times occupy a first position and at other times occupy a second position, a pair of conductors over which impulsesof energy of a selected polarity are at times supplied, a code following relay which is biased to a released position and is moved therefrom to a picked-up position when and only when energy fiows through the relay winding in a selected direction. circuit means effective only when the contacts of both of said transmitting and repeater relays are in their first position to connect the winding of said code following relay across said conductors so that impulses of energy of said selected polarity supplied over said conductors flows through the winding of said code following relay in said 24 selected direction, circuit means effective when the contacts of said transmitting relay are in their second position and the contacts of said pole changing relay are in their first position for connecting said source of direct current across said conductors independently of the winding of said code following relay so as to supply energy of said selected polarity to said conductors, circuit means effective when the contacts of said transmitting and pole changing relays are in their second position and the contacts of said repeater relay are in their first position for connecting said source of direct current across said conductors in series with the winding of said code following relay so as to supply ener y of the reverse of said selected polarity to said conductors and to cause energy to be supplied through the winding of said code following relay in the reverse of said selected direction, and means responsive to movement of a contact of said code following relay from its picked-up to its released position for supplying to said transmitting relay an impulse of energy effective to move the contacts of said transmitting relay from their first to their second position.

15. In a coded signaling system, in combination, a polarized transmitting relay having contacts which are moved to a normal or a reverse position according as energy of normal or reverse polarity is supplied to a winding of said relay, a repeater relay, a circuit including a normal contact of said transmitting relay for supplying energy to the winding of said repeater relay, a circuit including a back contact of said repeater relay for supplying energy of normal polarity to said transmitting relay, a pair of conductors over which impulses of energy are at times supplied, a code following relay, means including front contacts of said repeater relay and normal contacts of said transmitting relay for connecting the winding of said code following relay across said conductors, means including reverse contacts of said transmitting relay for connecting a source of energy across said conductors, and means for recurrently supplying impulses of energy of reverse polarity to said transmitting relay.

16. In a code signaling system, in combination, a polarized transmitting relay having contacts which are moved to a normal or a reverse position according as energy of normal or reverse polarity is supplied to a winding of said relay, a repeater relay, a circuit including a normal contact of said transmitting relay for supplying energy to the winding of said repeater relay, a circuit including a back contact of said repeater relay for supplying energy of normal polarity to said transmitting relay, a pair of conductors over which impulses of energy are at times supplied. a code following relay having contacts biased to a released position and movable therefrom to a picked-up position, means including front contacts of said repeater relay and normal contacts of said transmitting relay for connecting the winding of said code following relay across said conductors, means including reverse contacts of said transmitting relay for connecting a, source of energy across said conductors, and means responsive to movement of a contact of said code following relay from its picked-up to itsreleased position for supplying to said transmitting relay an impulse of energy of reverse polarity.

17. In a coded trackcircuit signaling system, in combination, a section of railway track having a first and a second track rail, a code following track relay at one end oi said section having a normally released contact which is picked up when and only when energy flows through the relay winding from the second to the first terminal thereof, a polarized transmitting relay having contacts movable between a normal and a reverse position, a repeater relay, a circuit including a normal contact of said transmitting relay for supplying energy to the winding of said repeater relay, means for recurrently supplying to said transmitting relay energy efiective to move the relay contacts to their reverse position, a circuit including a back contact of said repeater relay for supplying to the winding of said transmitting relay energy effective to move the relay contacts to their normal position, circuit means efiective only when the contacts of said transmitting relay are in their normal position and the contacts of said repeater relay are picked up for connecting the winding of said track relay across said track rails with the second terminal of the winding of said track relay connected to said first track rail, and circuit means effective only when the contacts of said transmitting relay are in their reverse position for connecting a source of direct current across said track rails independently of the winding of said track relay with the positive terminal of said source connected to said second track rail.

18. In a coded track circuit signaling system, in combination, a section of railway track having a first and a second track rail, a code following tnack relay at one end of said section having a normally released contact which is picked up when and only when energy flows through the relay winding from the second to the first terminal thereof, a polarized transmitting relay having contacts movable between a normal and a reverse position, means responsive to movement of the contacts of said track relay from their picked-up to their released position for supplying to the winding 01 said transmitting relay energy effective to move the contacts of said transmitting relay from their normal to their reverse position, circuit means eiiective only when the contacts of said transmitting relay are in their reverse position for connecting a source of direct current across said track rails independently of the winding of said track relay with the positive terminal of said source connected to said second track rail, a repeater relay, a circuit including a normal contact of said transmitting relay for supplying energy to the winding of said repeater relay, a circuit including a back contact of said repeater relay for supplying to the winding of said transmitting relay energy eflective to move the contacts or said transmitting relay from their reverse to their normal position, and means effective only when the contacts of said transmitting relay are in their normal position and the contacts of said repeater relay are picked up for connecting the winding of said track relay across said track rails with the second terminal of the winding of said track relay connected to said first track rail.

19. In a coded track circuit signaling system, in combination, a section of railway track, a code following track relay at one end of said section, a polarized transmitting relay having contacts movable between a normal position in which they connect the winding of said track relay across said track rails and a reverse position in which they establish a circuit for connecting a source of current across said track rails, a slow release repeater relay, a circuit including a normal contact of said transmitting relay for supplying energy to the winding of said repeater relay, means responsive to movement of the contacts of said track relay from their picked-up to their released position for supplying to the winding of said transmitting relay energy effective to move the contacts of said transmitting relay from their normal to their reverse position, and means including a back contact of said' repeater relay for supplying to the winding of said transmitting relay energy efiective to move the contacts of said transmitting relay from their reverse to their normal position.

20. In a coded track circuit signaling system, in combination, a section of railway track, a code following track relay at one end of said section, a polarized transmitting relay having contacts movable between a normal position in which they connect the winding of said track relay across said track railsand a reverse position in which they establish a circuit for connecting a source of current across said track rails, a slow release repeater relay, a circuit including a normal contact 01' said transmitting relay for supplying energy to the winding of said repeater relay, means responsive to movement of the contacts of said track relay from their picked-up to their released position for supplying to the winding of said transmitting relay over a circuit including a front contact of said repeater relay energy effective to move the contacts of said transmitting relay from their normal to their reverse position, and means including a back contact of said repeater relay for supplying to the winding of said transmitting relay energy effective to movethe contacts of said transmitting relay from their. reverse to their normal position.

mm H. mcnorson.

No references cited. 5 

